The Panoramic Camera Applied to 
Photo-Topographic Work. 



BY 



CHARLES WII*L, WRIGHT, 

WASHINGTON. D. C. 



A Paper Read before the American Institute of Mining 

Engineers, at the Toronto Meeting, 

July, 1907. 



AUTHOR'S EDITIOK 
190 8. 




SUBJECT TO REVISION. 



WC&I. -t*5T ****8 lm w « ». , .^C 



[TRANSACTIONS OF THE AMERICAN INSTITUTE OF MINING ENGINEERS.] 

The Panoramic Camera Applied to Photo-Topographic 

Work.* 



yf#> 



BY CHARLES WILL WRIGHT, WASHINGTON, D. C. 

(Toronto Meeting, July, 1907.) 

I. Introduction. 



The application of the camera as an adjunct to topographic 
mapping began practically with its invention, and it has been em- 
ployed with varying success since that time. With the excep- 
tion of the camera to be described, the plate-camera has been 
universally used in this work, thus giving a projection of the 
area photographed on a flat surface. From such projections or 
photographs, by the rules of geometry and of perspective, 
points defining topographic features and seen from at least two 
camera-stations may be projected upon a ground-plane — the 
map. 1 

In 1904 I employed the plate-camera for this purpose in 
Alaska, but found that the labor necessary to plot the maps, 
even in a general way, was long and tedious. In 1905 a small 
Eastman panoramic camera was fitted with spirit-levels, a sight- 
alidade and a transparent scale, introduced inside the camera 
to register the degree-points in the sky-line of the film-nega- 
tive; also, arrows to indicate the horizon-line. This was, on 
the whole, successful; but the details in the topography were 
not brought out in the views with sufficient clearness, and the 
photographs were too small. These difficulties were overcome 
by obtaining a larger and more carefully constructed instru- 
ment, which was satisfactorily employed in the field during the 
year 1906. 

A panoramic view is made up of an integral number of per- 
spective views upon flat surfaces, and logically is the most ac- 

* Published by permission of the Director of the XL S. Geological Survey. 

1 Stanley, H. M. Photographic and Co-ordinate Surveying, Trans., xx., 740 
to 766 (1891). Also, Flemer, H. L. Photographic Methods and Instruments, 
Report U. S. Coast and Geodetic Survey, pt. 2, app. 10, pp. 619 to 735 (1897). 

[1] 






*fl ■*>"*, t •;!!*& 



102 



THE PANORAMIC CAMERA. 



curate and direct means to obtain an impression of a field of 
view for purposes of mapping. In the perspective view, only 
one line — the vertical center-line — records the direct azimuth 
or bearing of points within its perspective; and all other 
points must be determined by geometric projection, thus intro- 
ducing an element of error. In the panoramic view, where the 
negative is everywhere equidistant from the camera lens and 
in its focal plane, the positions of all points are in direct hori- 
zontal angular relation to one another on the negative, as in 
nature ; and by introducing a degree-scale which, at the time 
of exposure, is photographed in the sky-line of the negative, 
the bearing of any point relative to any other point within the 
view may be read from it directly. 



^^~ r ~-~tJpP eI Film 



Guide ~~- 



Vertical Scale 







Fig. 1. 



-Sketch of Panoramic Camera with Front Eemoved, Showing 
Positions of Horizontal and Vertical Scales. 



The underlying principles of this method, therefore, do not 
differ essentially from those used in plane-table surveying. In 
all cases it is necessary either to have two points, within the 
area to be mapped, between which the horizontal distance has 
been determined ; or, better, to have a preliminary triangula- 
tion of a number of the prominent points or peaks within the 
area which will form the base for the map, so that these deter- 
mined triangulation-points may form tie-points for the camera- 
stations. It is then possible within certain areas to do the 
greater portion of the mapping with the aid of the camera 
alone. As in plane-table work, the traversing of trails and 
wagon-roads, and the determination of topographic stations, 
are more accurately made by an instrumental survey. 



By trait* lei 

DEC 15 WIS 



[2] 



THE PANORAMIC CAMERA. 

II. The Camera. 



103 



The camera best adapted for this purpose at present on the 
market is the Al Yista camera, Model 5 B, which takes a 5- 




Fig. 2. — The Panoramic Camera Fitted for Topographic Mapping. 

by 12-in. view, including an angle of 140° (Fig. 2). It consists 
of an oblong box, 6 in. by 6 in. by 11 in., fitted with a lens of 
fixed focus, which may be made to revolve at different speeds 

[3] 




[4] 




[5] 



106 



THE PANORAMIC CAMERA. 




Fig. 5. — Map or Rendu Glacier, Glacier Bay, Alaska. Plotted from 

Figs. 3 and 4. 




I 



PLAN 



SIDE ELEVATION 



front elevation 
Fig. 6. — Sketch of Framework for Plotting Directly from 
Photograph. 

[6] 



THE PANORAMIC CAMERA. 107 

within a half-circle, and with the introduction of apertures of 
various sizes allows the correct light- value for the exposure to 
be obtained. Retaining the film are two circular film-guides, 
so placed, one at the top and one at the bottom of the camera- 
box, that the film, in passing outside of them, will be in the 
focal plane of the lens at all points. For more exact work, a 
camera of this type should be constructed of metal, to elimi- 
nate the error which may be introduced by shrinkage of the 
wooden parts. 

To fit the camera for surveying, both a horizontal and a ver- 
tical scale should be so adjusted within the camera-box as to be 
photographed on the sensitized film at the time of exposure. To 
accomplish this, a narrow strip of celluloid graduated into de- 

2 y tz 
grees (1° = when r= focal length of lens) is glued to 

the lower circular film-guide in such a way that the degree- 
marks project J- in. above the guide. The sensitized film passes 
on the outside of this, and when the exposure is made the de- 
grees are photographed in the sky-line of the film. These de- 
gree-marks are nearly 0.1 in. apart on the negative ; and on an 
enlargement of two diameters, angular readings may easily be 
estimated to an accuracy of 5 minutes. 

On the sides of the upper and lower film-guides is attached 
a thin metal strip, 0.25 in. wide, in which wedge-shaped 
notches are made, the divisions (= -^ in. for the camera used) 
being equal to a hundredth part of the focal length of the lens 
(see Figs. 1, 3 and 4). These two vertical scales must be ad- 
justed so that the center-point marked on each strip will fall in 
the center of the camera-field or film, and a straight line con- 
necting these two points on the negative, after exposure, will 
thus establish the horizon-line. To the top of the camera-box 
two 60-second levels at right angles to each other are adjusted 
and a sight alidade is attached, in such a manner that its di- 
rection of sight coincides with a line extended from the center 
of the lens to the zero or center-point of the horizontal scale 
inside the camera. The bottom of the camera-box is fitted 
with three leveling-screws, adjustable to the transit-tripod. To 
make the camera more serviceable, and to eliminate the neces- 
sity of a transit at the camera-stations, a transit-plate with ver- 
nier may also be fitted to the camera-box; and from this all 

[7] 



108 THE PANORAMIC CAMERA. 

necessary angles can be read. From the photographs taken 
with a panoramic camera fitted with the above attachments it 
is possible to determine the positions, both horizontally and 
vertically, of all points within the area photographed. 

III. Adjustment. 

To determine whether the zero of the horizontal scale cor- 
responds to the point of sight taken with the alidade, and also 
to ascertain whether the center-marks of the vertical scale rep- 
resenting the horizon-line are correctly placed, the procedure 
is as follows : 

With the transit set up over a station from which a broad 
view may be obtained, sight on some prominent point and then 
take angular readings to other points and note several points of 
equal elevation to the station occupied. Set up the camera over 
this station, sight the attached alidade on the first point sighted 
with transit, and then take view. After development of the 
negative a comparison of the readings is made. If the zero of 
the horizontal scale does not fall directly over the point sighted 
with the alidade, shift the scale or alidade to the amount of 
difference indicated on the negative. If the points of equal 
elevation noted by the transit-readings do not fall on the hori- 
zon-line represented on the vertical scales, it is a simple matter 
to adjust either the scales or the levels until such is the case. 
To make this latter adjustment perfect may require several 
trials. 

A simpler way to adjust the vertical scales, and a test that 
should be made from time to time in the field, is to set up the 
camera on the shore-line of a lake or at sea-level and make an 
exposure; the horizon-line indicated by the vertical scales 
should coincide with the surrounding shore-line of the lake or 
the horizon-line of the sea. If this is not the case, the scales 
should be adjusted until harmony exists. 

With the present camera adjustments for determining the 
parallelism of the film to the axis on which the lens revolves 
cannot be made. A camera, however, is under construction in 
which this and other adjustments will be possible. 



[8] 



THE PANORAMIC CAMERA. 109 

IV. Field-Work. 

The accuracy and detail of the mapping depend largely upon 
the precision of the base work, the number of camera-stations 
occupied, and also the scale of the map. If a careful primary 
and secondary triangulation of an area has been made, and 
numerous stations have been established, one could enter the 
field with camera alone and complete the field-work of a fairly 
accurate topographic survey of that section in the same man- 
ner one would use a plane-table, but in a much shorter time. 
With the plane-table, most of the plotting is done in the field, 
with the camera the same work is done in the office ; with the 
plane-table one can occupy but one station at a time; with 
the camera, when plotting, one can practically occupy two or 
more stations at once and in this way simultaneously, from 
two or more points of view, see the area to be mapped. This 
latter circumstance is a strong factor in the identification of 
points. Again, when a mere reconnaissance-survey is to be 
made, the topographic work may be accomplished with the 
camera while the triangulation is advancing. By so doing, not 
only time is saved, but much information regarding the timber- 
limits and density of growth, and in some instances character- 
istics in land-sculpture and geologic structure, may afterwards 
be obtained from the photographs, all of which would be 
omitted by the usual method of mapping. For reconnaissance- 
work the camera is, therefore, especially to be recommended. 

All the triangulation-stations occupied by the transit should 
also be occupied by the camera, thus securing a check on the 
triangulation. In selecting camera-stations, those taken at low 
and moderate elevations are of greatest service as aids in draw- 
ing the topographic details, while those at high elevations are 
best for advancing the triangulation. In each case, however, 
it is necessary to have three previously-determined points in the 
field of view, preferably at wide angles, which may be sighted 
with the alidade on the camera from the station occupied, so 
that, from the angular readings taken, the position of the 
camera-station can be determined. The elevations of these in- 
termediate stations are noted from barometric readings and 
later are checked by determinations from the elevations of 
known points included upon the negative. The elevations of 
the triangulated points, where the transit is employed, are de- 

[9] 



110 THE PANORAMIC CAMERA. 

termined in the usual way by vertical angle-readings upon 
points of known elevation or at sea-level. 

It is hardly necessary to mention the advisability of erecting 
monuments or signals upon all stations so that they may be 
sighted from other and new stations. 

V. Plotting Maps from Photographs. 

It is first necessary to develop the film-negatives — the best 
plan being to do so in the field, so that a defective negative may 
be replaced by taking another view at once. Such failures, 
however, are not probable. During the past summer I took 
200 views under all conditions of weather, and not one of the 
negatives was defective. They were developed in the field, for 
the most part within a day or two after exposure; and several 
dozen, left undeveloped until my return to the office, some three 
months later, were developed with equally good results. 

A preliminary plotting of triangulation-points and camera, 
stations on the map should be done in the field, and traverses 
of trial- and shore-lines should be added. This is recommended 
to prevent the introduction of " holes " in the map, that is, 
small areas which cannot be accurately plotted in the office, 
because they were sighted from but one station, or were other- 
wise neglected. In the office, to facilitate the topographic plot- 
ting, enlargements are made from the negatives, which were 
5 by 12 in., to prints, 10 by 24 in. in size. As the horizontal 
and vertical scales are photographed on the negative at the 
time of exposure, no error is introduced by making these en- 
largements. The uneven contraction and expansion of photo- 
graphic paper is often a cause of error in plotting ; but if care 
is taken in developing and drying the prints, and if they are 
all made on the same kind of photographic paper, this error is 
only a slight one. To eliminate it, however, plotting may be 
done directly from the negatives. 

Having established a map-scale and plotted the triangulation- 
points, the camera-stations should next be determined. This is 
done by the three-point method, by which the angular readings 
to three or more determined points, taken from the station, 
either by a transit or read from the photograph, are plotted on 
a piece of tracing-paper. The lines indicating the angular 

[10] 



THE PANORAMIC CAMERA. Ill 

readings are placed over the respective points and the positions 
of the camera-stations thus located. 

The camera-stations being plotted on the map, one may next 
proceed to select numerous points common to two or more 
views from different stations, and to plot their positions by lines 
of intersection representing their respective hearings read from 
the horizontal scale on the photograph. 

To facilitate this work a T-square 1 ft. long is made, the 
vertical arm heing divided to correspond with the vertical scale 
of the photograph. The photograph is adjusted to a drawing- 
hoard 12 by 24 in. in size, so that the center-line of the ver- 
tical scales coincides with the center-division marked on the 
T-square. (See Fig. 7.) On the map a line is drawn from the 
respective camera-station in the direction sighted at the time 
the photograph was taken, and by the aid of a protractor, and 
angular readings taken with the T-square from the horizon- 
tal scale, the directions of all points may be plotted. When the 
position of any point has been determined by the intersection 
of its lines of direction from two or more stations, its relative 
elevation maybe obtained by multiplying the number of divisions 
on the T-square above or below the center-line by the horizon- 
tal distance of the point, measured in feet, and dividing by 100, 
as the divisions represent hundredths of the focal length for 
the photograph. (The focal length or radius for the enlarged 

2 
panoramic photograph is obtained from the formula r = — iZ, 

7% 

where H = J- of the circumference of circle or distance meas- 
ured between 90° on the horizontal scale of the enlarged pho- 
tograph). This result is added to the elevation of the -camera- 
station above sea-level and the sum is the elevation of the point. 
Thus, if a mountain-peak is 20 divisions above the center- 
line on the vertical scale and the horizontal distance measures 

8,000 ft., then its relative altitude is 2 ° * 8 ' 0QQ = 1,600 ft.; 

this added to the elevation of the camera-station gives the total 
elevation of the peak above sea-level. (In computing the ele- 
vation of distant points the correction for curvature of the earth 
and refraction should be added.) 

When plotting, the photographs showing the same area from 

[ii] 



112 



THE PANORAMIC CAMERA. 



two stations are set up on the drawing-table, as shown in Fig. 
7, and points seen from both stations are numbered directly on 
the photographs, the same numbers being used to indicate the 
points on the map. 

The protractor used in this work was of card-board, 10 
in. in diameter, with the central portion cut out. This was 
oriented on the map over the camera-station and made fast 
with thumb-tacks. A narrow scale, 10 in. long, divided into 
units of the map-scale, and fitted with a pin-point at the mark, 
served as a protractor-arm as well as a scale for measuring the 
horizontal distance. This arrangement is shown in Fig. 7. 

To obviate the necessity of orienting the protractor for each 
station, and to facilitate plotting, a parallel movable engineers' 
protractor may be used to advantage. As this protractor has a 
fixed orientation it is necessary to determine the azimuth for 



Horizontal Scale 



T-Square-x_ 




F IG . 7.— Sketch Showing Arrangement for Plotting of Map from 

Photographs. 

the zero-point on each photograph and to adjust the horizon- 
tal scale so that the direct azimuth readings may be taken 
from the photographs. 

After a sufficient number of characteristic points have been 
plotted upon the map and their elevations noted, it is a simple 
procedure to introduce the lines of contour by the aid of the 
photographs. By using the above method an experienced to- 
pographic draftsman can complete an expressive map of the 
land-sculpture of an area from photographs in the office. 

Both the plotting of points and the determination of their 
elevation may be done graphically as follows : 

Construct a framework, consisting of 3 bars, equal in length 
(about 5 in.), attached to a curved strip of metal sheeting, 
of the size of the photograph, shown in Fig. 6. At the 
junction of the 3 bars representing the radii of the arc, at- 
tach a pin-point; the distance from pin-point to outer surface 

[12] 



THE PANORAMIC CAMERA. 



113 



of curved metal sheet should be equal to the determined focal 
length for the photographs from which the map is to be plotted. 
On the photograph, project the points to be plotted to its base 
(bottom of photograph). Fasten this photograph face out to 
the framework and place pin-point on the same over the sta- 
tion-point on the map and then orient it in the photo direc- 
tion. Project the points at base of photograph on the map, 
indicating them by numbers corresponding to those on the pho- 
tograph. In this manner the direction of each point is plotted 
directly from the photographs. 

To ascertain the altitude of points on the photograph rela- 
tive to the camera-station we have this proportion : The meas- 
ured distance, y, of point on photograph above or below the 




Fig. 8.— Diagram foe Determining Eeevation of Points. 



horizontal line is to the determined focal length for photo- 
graph, /, as the elevation of the point E above or below camera- 
station is to its horizontal distance, x, from the camera-station. 
This proportion, y : f = E : x, gives xy = Ef, which is the 
formula for a hyperbola in which x and y are the variable and 
E and / the constant factors. 

To construct the diagram, divide the horizontal axis of a 
rectangular co-ordinate- system into units of the map-scale; 
from this, at points representing intervals of 1,000 ft. horizontal 
distance, erect vertical lines, on which the computed lengths of 
y for each 100 ft. elevation at the respective horizontal dis- 
tances are indicated. By connecting the points which repre- 
sent the same elevation on these vertical lines of the diagram, 
hyperbolic curves are formed (see Fig. 8), each curve represent- 

[13] 



114 THE PANORAMIC CAMERA. 

ing points of equal elevation at their respective horizontal dis- 
tances. With a diagram thus constructed, we can scale the 
horizontal distance of a point directly and also measure its 
elevation, relative to the camera-station, by transferring, pref- 
erably with a pair of dividers, the distance y from the photo- 
graph to the diagram, directly above the point indicating its 
horizontal distance. The practicability of this graphic method 
has not been tested ; but, though it may lack in accuracy, it 
will undoubtedly facilitate and greatly shorten the work of 
plotting the maps. 

VI. Accuracy or Method. 

The two photographs, Figs. 3 and 4, may serve to illustrate 
the panoramic method. These views are of Rendu Glacier, in 
Glacier Bay, Alaska. The peaks with a triangle over them 
are triangulation-points determined in 1892 by Professor H. F. 
Reid, whose map was used as a base. The two camera-sta- 
tions occupied, on opposite sides of the inlet, were located by 
transit-readings on the triangulation-points. These points and 
stations were first plotted on the accompanying map, Fig. 5 ; 
the positions of numerous points represented on each photo- 
graph were determined by the above method, and a map suffi- 
ciently accurate for the intended purpose was thus constructed. 

The maximum difference in elevation of a point measured on 
photographs from two or more camera-stations seldom exceeds 
10 ft. for a horizontal distance of one mile. Determinations of 
the two triangulation-points shown in the accompanying views 
gave the following results : 

Triangulation Pt. 1, from Sta. A. Horizontal dist. = 31,500 
ft. Elevation = 4,934 ft. 

Triangulation Pt, 1, from Sta. B. Horizontal dist. = 25,000 
ft. Elevation = 4,906 ft. 

A difference of 28 ft. in a distance of 5 miles. 

Triangulation Pt. 2, from Sta. A. Horizontal dist. = 14,500 
ft. Elevation = 4,868 ft. 

Triangulation Pt. 2, from Sta. B. Horizontal dist. = 18,400 
ft. Elevation = 4,842 ft. 

A difference of 26 ft. in a distance of 3 miles. 



[14] 



THE PANORAMIC CAMERA. 115 

VII. Advantages of the Panoramic Camera Method. 

Photography cannot replace instrumental topographic sur- 
veying, and, in many areas, cannot be used at all ; yet experi- 
ence has shown it to be a valuable adjunct in nearly all sur- 
veys. The topographic features of an area will necessarily 
determine the method to be employed in its mapping. A flat, 
rolling plain cannot be mapped in the same manner as a rug- 
ged mountainous region, or a heavily timbered area where 
broad views cannot be obtained. Areas of bold topography 
with sharp or often rounded summits and little timber, such as 
are encountered in the western States and Alaska, are most 
advantageously mapped by the camera method. To make a 
plane-table survey of such an area requires the expenditure of 
much time in the field in constructing the map, and the ex- 
pense of a large field-party. The conditions of weather which 
exist along the western coast and in Alaska are such that the 
summits are enveloped in a cloud of fog, often during the 
greater portion of the day. When the view is clear for a short 
time only, a photograph of the surrounding country may be 
taken, thus completing in a fraction of an hour the work at a 
station which would require many hours or even days by the 
plane-table method. It should be noted that alidade-reading 
and note-taking from a mountain-top in Alaska on the usual 
cold, foggy day, with a still colder wind blowing, is by no 
means comfortable, and even the best topographers are inclined 
to hurry their work. In this manner, some portions of an area 
are more carefully mapped than others. Having the photo- 
graphs of an area with the bearings of all points registered 
directly above them, the plotting of the map can be done with 
more agreeable surroundings in the office, where all conven- 
iences are at hand, and thus a map can be constructed of more 
uniform accuracy, and with as much detail as desired. If this 
or a similar graphic method of mapping were applied in certain 
regions a great deal would be saved in both time and expense, 
compared with topographic surveying as generally practiced. 



[15] 



116 THE PANORAMIC CAMERA. 

VIII. Comparison of Panoramic Camera Method with 
Other Photographic Methods. 

In the present practice of photo-topography a photo-theo- 
dolite or similar instrument is employed. This consists of a 
specially prepared plate-camera with a fixed-focus lens adjusted 
to a horizontal transit-circle. Attached to the top of the 
camera-hox is a telescope with vertical circle for the reading of 
vertical angles. At the back of the camera and directly in 
front of the sensitized plate are two cross-hairs, the one form- 
ing the vertical center-line and the other the horizon-line. In- 
side the camera is a flat magnetic needle attached to a disk, to 
which a vertical transparent scale is adjusted. This revolves 
directly in front of the sensitized plate so that when the expo- 
sure is made the magnetic bearing of the view is photographed 
upon it. With this instrument a group of eight views are 
necessary to complete a panorama, and the angular direction 
of each view must be read on the horizontal transit-plate and 
noted. Another disadvantage of the photo-theodolite is its 
weight and bulk, besides the limited number of plates which 
may be taken on a trip and the necessity of reloading the plate- 
holders. With the panoramic camera the daylight-loading 
films are used, which eliminate the danger of breakage, lessen 
the weight to be carried and permit development in the field 
directly after exposure, in a daylight developing-tank. 

The plotting of a map from the views taken by the photo- 
theodolite is a long and tedious process (though possessing no 
special difficulties), and the office work necessary to complete 
the map is many times greater than that required for the same 
amount of mapping by the panoramic camera. 



[16] 



Ill I'll 

021 605 293 < 



